Old-Growth Forest Dynamics After Fire and Drought in the Sierra Nevada, California, USA

Understanding forest ecosystems is important because forests cover approximately one-third of Earth’s land area, store half of Earth’s carbon, shelter half of Earth’s species, and absorb a quarter of new anthropogenic carbon emissions, slowing climate change. This dissertation provides insight into future forest habitat, fuels, species composition, and structure by investigating what happens to snags, seedlings, and trees in an old-growth forest after a low- to moderate-severity fire. Chapter II explores how low- to moderate-severity fire changes snag fall rates. Predicting how long snags will remain standing after fire is essential for managing habitat, understanding chemical cycling in forests, and modeling forest succession and fuels. Pre-fire snags––which tend to be preferred habitat because they include more large-diameter snags in advanced stages of decay––were at least twice as likely to fall as new snags within 3–5 years after fire. Pre-existing snags were most likely to persist five years after fire if they were \u3e 50 cm in diameter, \u3e 20 m tall, and charred on the trunk to heights above 3.7 m. Chapter III examines the effects of fire severity and microclimate on conifer regeneration after fire. Available seed, lower burn severity on the forest floor, more fire-caused tree mortality, and earlier snowmelt during the germination year gave Pinus lambertiana seedlings an advantage over Abies concolor seedlings, suggesting that lower-severity fire could naturally shift forest species composition toward Pinus species, which are more resistant to fire and drought. Chapter IV investigates the effects of lower-severity fire on tree growth by analyzing the tree-ring widths of seven mixed-conifer species throughout the Sierra Nevada. Post-fire growth patterns were not substantially different from growth fluctuations at adjacent unburned plots, suggesting that reintroducing lower-severity fire to forests where fire has been excluded over the last century will not prevent surviving trees from attaining pre-fire growth rates within five years after fire. Chapter V focuses on recruitment of large-diameter trees after fire, analyzing how local post-fire mortality within tree neighborhoods impacts post-fire radial growth of surviving trees. Cause of mortality influenced the relationship between neighborhood change and the growth of surviving trees, and this relationship was different for A. concolor compared to P. lambertiana, suggesting that species differences in cause of mortality could affect the species composition of future large-diameter tree populations. These findings demonstrate that low- to moderate-severity fire can promote Pinus seedlings and trees, exemplifying the concept that ecosystems shift toward species composition and structure that maximize resilience to challenging climate and disturbance regimes. This research was possible because of the existence of a long-term, spatially explicit, observational old-growth forest dataset with annual resolution

DNA: From rigid base-pairs to semiflexible polymers

The sequence-dependent elasticity of double-helical DNA on a nm length scale can be captured by the rigid base-pair model, whose strains are the relative position and orientation of adjacent base-pairs. Corresponding elastic potentials have been obtained from all-atom MD simulation and from high-resolution structural data. On the scale of a hundred nm, DNA is successfully described by a continuous worm-like chain model with homogeneous elastic properties characterized by a set of four elastic constants, which have been directly measured in single-molecule experiments. We present here a theory that links these experiments on different scales, by systematically coarse-graining the rigid base-pair model for random sequence DNA to an effective worm-like chain description. The average helical geometry of the molecule is exactly taken into account in our approach. We find that the available microscopic parameters sets predict qualitatively similar mesoscopic parameters. The thermal bending and twisting persistence lengths computed from MD data are 42 and 48 nm, respectively. The static persistence lengths are generally much higher, in agreement with cyclization experiments. All microscopic parameter sets predict negative twist-stretch coupling. The variability and anisotropy of bending stiffness in short random chains lead to non-Gaussian bend angle distributions, but become unimportant after two helical turns.Comment: 13 pages, 6 figures, 6 table

Writing Center: Impact analysis Fall 2014 to Fall 2018

The Utah State University (USU) Writing Center is dedicated to empowering students to express their knowledge and ideas in writing. Their approach promotes academic inquiry, critical thinking, and expressions of diversity. While research and evaluation suggest that the Writing Center significantly impacts student academic performance, the impact on student persistence is not yet clear. This report explores the association between USU’s Writing Center and students’ persistence toward graduation. METHODS: Students’ Writing Center use was captured through student log-ins at writing appointments. Students who had a record of using the Writing Center were compared to similar students who did not have a record of Writing Center use. Students were matched for comparison using prediction-based propensity score matching. Students were matched with non-users based on their persistence predication and their propensity to participate. FINDINGS: Students were 97% similar following matching. Participating and comparison students were compared using difference-in-difference testing. Students who used the Writing Center were significantly more likely to persist at USU than similar students who did not use the Writing Center (DID = 0.031, p \u3c .001). The unstandardized effect size can be estimated through student impact. It is estimated that Writing Center resources and services assisted in retaining 17 (CI: 3 – 32) students each year who were otherwise not expected to persist

A two-dimensional Kolmogorov-Smirnov test for crowded field source detection: ROSAT sources in NGC 6397

We present a two-dimensional version of the classical one-dimensional Kolmogorov-Smirnov (K-S) test, extending an earlier idea due to Peacock (1983) and an implementation proposed by Fasano & Franceschini (1987). The two-dimensional K-S test is used to optimise the goodness of fit in an iterative source-detection scheme for astronomical images. The method is applied to a ROSAT/HRI x-ray image of the post core-collapse globular cluster NGC 6397 to determine the most probable source distribution in the cluster core. Comparisons to other widely-used source detection methods, and to a Chandra image of the same field, show that our iteration scheme is superior in measuring statistics-limited sources in severely crowded fields.Comment: 12 pages, 6 figures, 6 tables. Accepted by MNRA

Line profile variability in the spectra of Oef stars: II. HD192281, HD14442 and HD14434

We present the very first analysis of the spectroscopic variability of the three rapidly rotating Oef stars HD192281 (O5(ef)), HD14442 (O5.5ef) and HD14434 (O6.5(ef)). Radial velocities of the HeII lambda 4541 line reveal no evidence of binarity on time scales of a few days, or from one year to the next, for any of the targets. The HeII lambda 4686 double-peaked emission and, to some extent, the Hbeta absorption line display significant profile variability in the spectra of all three stars. Data gathered during different observing runs spread over six years reveal a rather stable time scale for HD192281 and HD14442, whereas the variability pattern changes significantly from one year to the other. The case of HD14434 is less clear as no obvious time scale emerges from our analysis. In a temptative way to interpret this variability, stellar rotation remains a possible clock for HD192281 and HD14442. However, currently available models addressing stellar rotation fail to explain some crucial aspects of the observed variability behaviour, which appear to be even more complex in the case of HD14434.Comment: 15 pages, 12 figures (8 postscript and 4 gif), accepted by A&

Analysis of the astray/robo2 Zebrafish Mutant Reveals that Degenerating Tracts Do Not Provide Strong Guidance Cues for Regenerating Optic Axons

During formation of the optic projection in astray/robo2 mutant zebrafish, optic axons exhibit rostro-caudal pathfinding errors, ectopic midline crossing and increased terminal arbor size. Here we show that these errors persist into adulthood, even when robo2 function is conditionally reduced only during initial formation of the optic projection. Adult errors include massive ectopic optic tracts in the telencephalon. During optic nerve regeneration in astray/robo2 animals, these tracts are not re-populated and ectopic midline crossing is reduced compared to unlesioned mutants. This is despite a comparable macrophage/microglial response and upregulation of contactin1a in oligodendrocytes of entopic and ectopic tracts. However, other errors, such as expanded termination areas and ectopic growth into the tectum, were frequently re-committed by regenerating optic axons. Retinal ganglion cells with regenerating axons re-express robo2 and expression of slit ligands is maintained in some areas of the adult optic pathway. However, slit expression is reduced rostral and caudal to the chiasm, compared to development and ubiquitous overexpression of Slit2 did not elicit major pathfinding phenotypes. This shows that (1) there is not an efficient correction mechanism for large-scale pathfinding errors of optic axons during development; (2) degenerating tracts do not provide a strong guidance cue for regenerating optic axons in the adult CNS, unlike the PNS; and (3) robo2 is less important for pathfinding of optic axons during regeneration than during development

Food Insecurity and Eating Disorder Pathology

Objective: The primary aim of this study was to investigate eating disorder (ED) pathology in those living with food insecurity. A secondary aim was to investigate whether any-reason dietary restraint, weight self-stigma, and worry increased as level of food insecurity increased. Method: Participants (N = 503) seeking food from food pantries completed questionnaires assessing level of food insecurity, demographics, ED pathology, dietary restraint, weight self-stigma, and worry. Results: Consistent with hypotheses, participants with the highest level of food insecurity (i.e., adults who reported having hungry children in their household) also endorsed significantly higher levels of binge eating, overall ED pathology, any-reason dietary restraint, weight self-stigma, and worry compared to participants with lower levels of food insecurity. Contrary to hypotheses, compensatory behaviors also increased as level of food insecurity worsened. Overall, 17% of those in the child hunger food insecurity group reported clinically significant ED pathology. Discussion: This is the first study to assess the full spectrum of ED pathology in a low income, marginalized population with food insecurity. Given that food insecurity is a global concern, results from this study suggest that greater attention to the association between ED pathology and food insecurity is warranted by researchers around the world

Shrub Communities, Spatial Patterns, and Shrub-Mediated Tree Mortality following Reintroduced Fire in Yosemite National Park, California, USA

Shrubs contribute to the forest fuel load; their distribution is important to tree mortality and regeneration, and vertebrate occupancy. We used a method new to fire ecology—extensive continuous mapping of trees and shrub patches within a single large (25.6 ha) study site—to identify changes in shrub area, biomass, and spatial pattern due to fire reintroduction by a backfire following a century of fire exclusion in lower montane forests of the Sierra Nevada, California, USA. We examined whether trees in close proximity to shrubs prior to fire experienced higher mortality rates than trees in areas without shrubs. We calculated shrub biomass using demography subplots and existing allometric equations, and we developed new equations for beaked hazel (Corylus cornuta ssp. californica [A. de Candolle] E. Murray) from full dissection of 50 stems. Fire decreased shrub patch area from 15.1 % to 0.9 %, reduced live shrub biomass from 3.49 Mg ha−1 to 0.27 Mg ha−1, and consumed 4.41 Mg ha−1 of living and dead shrubs. Distinct (non-overlapping) shrub patches decreased from 47 ha−1 to 6 ha−1. The mean distance between shrub patches increased 135 %. Distances between montane chaparral patches increased 285 %, compared to a 54 % increase in distances between riparian shrub patches and an increase of 267 % between generalist shrub patches. Fire-related tree mortality within shrub patches was marginally lower (67.6 % versus 71.8 %), showing a contrasting effect of shrubs on tree mortality between this forest ecosystem and chaparral-dominated ecosystems in which most trees are killed by fire

Cognitive behavioural therapy for anxiety disorders in children and adolescents

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: To carry out a meta‐analysis of identified studies to determine whether CBT leads to remission of 1) the primary child/adolescent anxiety disorder and 2) all anxiety diagnoses, and/or 3) a clinically significant reduction in anxiety symptoms in comparison with passive (waiting list) controls, active controls, treatment as usual, or medication. To determine the comparative efficacy of CBT alone, and the combination of CBT and medication, versus drug placebo. To determine whether post‐treatment gains of CBT are maintained at longer‐term follow‐up. To describe the age range of participants included in CBT trials in order to determine the age of the youngest participants. To determine whether CBT for anxiety leads to a clinically significant reduction in depressive symptoms, and/or improvements in global functioning. To carry out subgroup analyses of different types of CBT according to 1) amount of therapist contact time; and 2) delivery format (child‐focused individual, group, and with/without family involvement, and parent‐delivered). To carry out a subgroup analysis of CBT for children and adolescents with ASD and for children and adolescents with intellectual impairments

Evolutionary biology and anthropology suggest biome reconstitution as a necessary approach toward dealing with immune disorders

Industrialized society currently faces a wide range of non-infectious, immune-related pandemics. These pandemics include a variety of autoimmune, inflammatory and allergic diseases that are often associated with common environmental triggers and with genetic predisposition, but that do not occur in developing societies. In this review, we briefly present the idea that these pandemics are due to a limited number of evolutionary mismatches, the most damaging being ‘biome depletion’. This particular mismatch involves the loss of species from the ecosystem of the human body, the human biome, many of which have traditionally been classified as parasites, although some may actually be commensal or even mutualistic. This view, evolved from the ‘hygiene hypothesis’, encompasses a broad ecological and evolutionary perspective that considers host-symbiont relations as plastic, changing through ecological space and evolutionary time. Fortunately, this perspective provides a blueprint, termed 'biome reconstitution', for disease treatment and especially for disease prevention. Biome reconstitution includes the controlled and population-wide reintroduction (i.e. domestication) of selected species that have been all but eradicated from the human biome in industrialized society and holds great promise for the elimination of pandemics of allergic, inflammatory and autoimmune diseases